According to a conventional linear motion ball bearing of this type, generally a ball return hole is formed axially in a bearing body to let balls circulate in an axial direction, and a machining for curved surface is performed to connect end portions of the return hole and a loaded ball groove formed in the bearing body, and further a return cap having a ball turning groove for changing the direction of ball by 180.degree. is applied to each end portion. Besides, in order to prevent balls from falling off when the bearing body is pulled out from a rail base, it is necessary to provide a ball retainer separately.
It has been proposed to use a side face of a bearing body as part of a ball return hole in place of forming a ball return hole axially in the bearing body, as disclosed in Japanese Patent Laid-Open Publication No. 58225/84. Even in this proposed construction, however, it is still necessary that each end portion of the ball return hole and a loaded ball groove formed in the bearing body be covered with a return cap having a ball turning groove. Besides, a separate provision of a ball retainer is also required as before.
Thus, these conventional techniques are disadvantageous in that the number of parts increases and troublesome machinings are required.